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al_lock_bitmap(3)                                            al_lock_bitmap(3)

NAME
       al_lock_bitmap - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              ALLEGRO_LOCKED_REGION *al_lock_bitmap(ALLEGRO_BITMAP *bitmap,
                 int format, int flags)

DESCRIPTION
       Lock an entire bitmap for reading or writing.  If the bitmap is a
       display bitmap it will be updated from system memory after the bitmap
       is unlocked (unless locked read only).  Returns NULL if the bitmap
       cannot be locked, e.g.  the bitmap was locked previously and not
       unlocked.

       Flags are:

       o ALLEGRO_LOCK_READONLY - The locked region will not be written to.
         This can be faster if the bitmap is a video texture, as it can be
         discarded after the lock instead of uploaded back to the card.

       o ALLEGRO_LOCK_WRITEONLY - The locked region will not be read from.
         This can be faster if the bitmap is a video texture, as no data need
         to be read from the video card.  You are required to fill in all
         pixels before unlocking the bitmap again, so be careful when using
         this flag.

       o ALLEGRO_LOCK_READWRITE - The locked region can be written to and read
         from.  Use this flag if a partial number of pixels need to be written
         to, even if reading is not needed.

       'format' indicates the pixel format that the returned buffer will be
       in.  To lock in the same format as the bitmap stores it's data
       internally, call with al_get_bitmap_format(bitmap) as the format or use
       ALLEGRO_PIXEL_FORMAT_ANY.  Locking in the native format will usually be
       faster.

              Note: While a bitmap is locked, you can not use any drawing
              operations on it (with the sole exception of al_put_pixel(3) and
              al_put_blended_pixel(3)).

SEE ALSO
       ALLEGRO_LOCKED_REGION(3), ALLEGRO_PIXEL_FORMAT(3), al_unlock_bitmap(3)

Allegro reference manual                                     al_lock_bitmap(3)